Combustion chamber



July 1 3, 1943. R. H. SHEPPARD :CDMBUSTI'ON CHAMBER Filed Nov. 1, 1941 Hjzzmwdje ara Patented July 13, 1943 UNITED STATES PATENT OFFICECOMBUSTION CHAMBER Richard H. Sheppard, Hanover, Pa.

Application November 1, 1941, Serial No. 417,532

Claims.

This invention relates to Diesel engines, and has for its general objectthe provision of an improved combustion chamber having more efficientturbulence during the injection period.

The primary object of my invention is to provide an arrangement ofcombustion chamber and cylinder which reduces the amount of solid fuelimpinging against the enclosing surfaces thereby improving thecombustion by reducing smoldering and resulting carbon deposit.Smoldering, indicated by smoky combustion, is chiefly due to lack ofair, at the point of contact with the surfaces, and therefore byincreasing the ratio of air to the portion of solid fuel touching thehot surfaces I reduce the smoldering and without changing the ratio oftotal air to total fuel charge.

A second object of this invention is to increase the power whiledecreasing the exhaust smoke by adding a third and smaller throatworking in opposition to the other two throats. This provides furtherturbulence in the combustion chamber and more important it prevents fuelfrom the injector from being swept on to the combustion chamber wall bythe main swirl provided by the two large throats.

A third object of the invention is to eliminate or greatly reduce thetremendous pressure exerted by a tightly fitting block tending to forceapart the head and block with attendant loss of pressure. This isaccomplished by making a portion of the chamber non-rigid so it maycompress at operating temperature and expand to full length when cooler.

A specific object is to provide a combustion chamber arrangement wherebya portion of the fuel charge and particularly the larger droplets offuel occuring at full load are directed into the upper central portionof the cylinder. A further specific object is to provide a combustionchamber in which the fuel charge is insulated from the surface by alayer of revolving air which is turbulent on its descending side.

A still further specific object is to form in the chamber block anoutside annular groove and an inside annular groove so that the chamberblock or plug may be made exactly the same length as the hole into whichit fits, thereby avoiding the building up of carbon deposits as occursif the block is a few thousandths short to allow for expansion atextreme temperatures.

An important object is to provide a combustion chamber plug to besubstituted in existing engines having spherical or cylindricalcombustion chambers to increase the efficiency of such engines.

In the drawing:

Figure 1v is a vertical sectional view of the upper part of an engineshowing the cylinder and combustion chamber.

Figure 2 is an enlarged top plan view of the chamber plug.

Figure 3 is a central section through Figure 2.

In Figure 1 the engine block i0 is shown as having a cylinder II andcylinder head l2, with a combustion chamber M located in the head [2.The combustion chamber is preferably of spherical shape and has at thetop a fuel injection nozzle I5 which is adapted to inject a jet of fuelhaving its axis IS approximately in the vertical diameter of thechamber.

The upper part of the combustion chamber is formed by the hemisphericaltermination ll of the bore IS in the cylinder head I2 and the lower partis a complementary cavity in the upper face of what may be termed athroat block or plug l9 fitting in the bore and in which it is held byits bottom face being engaged by the top of the cylinder block; a screw20 on the edge of the plug, as best shown in Figure 2, prevents rotationof the plug from its preferred angular position. Although a sphericalchamber is preferred I find that a chamber having circular cross sectionin planes parallel to the axis of the cylinder is also satisfactory.

The throat block or plug I9 is provided, in addition to the new thirdthroat 2|, with a main throat 22 and an auxiliary throat 24, the outerwall 23 of the main throat being tangential to the surface of thechamber whereby air rushing through will rotate in the chamber about itsaxis which in the drawing is a horizontal axis. The auxiliary throat 26is at a slight angle to the tangent of the chamber wall and ispositioned to direct the outgoing charge toward the center 25 of theupper part of the cylinder and has its orifice 2'! located to receivedroplets from the injector nozzle l5, that is, the axis of the fuel jetpasses through the orifice 21. The throat 24 is positioned to produce alayer of air within the layer of air created by the air rushing throughthe main throat 22 into the chamber. Whether the combustion chamber isspherical or is cylindrical in shape the throat block is positioned forbest results with the axis of the throat 24 in a radial plane of thecylinder and the third throat 2| and main throat 22 are preferably butnot necessarily located with their axes in the same plane whereby thefuel charge is directed toward the center of the cylinder. As shown inFigures 1 and 3, the axis of the third throat is vertical, the mainthroat lies at an angle of 72 and that of the second or auxiliary throatis less steep, lying at an angle of 40.

The main and auxiliary throats discharge air from the cylinder into thecombustion chamber to revolve in the same direction but the smallerthird throat opposes this motion and creates turbulence on the right ordescending side of the outer air layer.

Under full load, a. large percentage of the fuel reaches the oppositeside of the combustion chamber and enters the throat 24 without beingatomized, so that the out-rushing fuel charge carries, or at leaststarts, these relatively large droplets directly toward the center .ofthe cylinder, thus producing efficient combustion by reducing to aminimum the amount of solid fuel contacting the enclosing walls. Thethroat 24 is preferably positioned so that its axis intersects thecylinder axis 25 at a point spaced from the cylinder head a distance notmuch greater than the length of the throat. The third throat, byopposing deflection of these droplets from the entry end of the secondthroat, materially aids inthe desired avoidance of color in the exhaustdischarge.

In the plan view, Figure 2 showing the preferred relative position ofthe parts, it will'be seen that the vertical plane 29 containing thevertical axis N5 of the combustion chamber bisects all three throats andlies between the exhaust valve 38 and the intake valve 32. The chamberwith only the main and auxiliary throats is an excellent design but thethird throat 2i increases the power and provides a more efficient andquiet combustion as indicated by the decrease in exhaust smoke, which atordinary loads is substantially invisible, if not actually so.

The grooves-'34 and with the slight bevel 3B permit the making of theplug or block of the exact length of the bore I8 which receives it. Whena block is made shorter than the length of the bore, the remedy is onlya temporary one,

because of the building up of carbon deposits, during the startingprocess, which soon fill the space. By means of the slot or groove 34cut inward from the outside of the block and the adjacent slot or groove35 in the combustion chamber itself the block loses its absoluterigidity and may compress in length a few thousandths .of an inchwithout damage to itself or exerting damaging pressure to separate'thebody and head. Without these grooves the combustion chamber plug, beinghotter than the head which. surrounds it, expanded a greater amounttending to force apart the cylinder block and its head so that theremight be a loss of gases with consequent loss of power. It is importantto'note that the deformation is temporary as although the compressionchanges the length of the combustion chamber plug is constant so it istight in the head when cooled as when the engine is in operation.

The high efficiency of combustion obtained by my engine under all loadsis believed to be due to the fact that a minimum of solid fueltouchesthe hot enclosing surfaces and this for two reasons: first, the airentering the combustion chamber through the throat 22 during compressionforms an insulating layer of air between the surface of the chamber andthe atomized fuel from the fuel nozzle and the mainfuel charge iscontained mainly in an inner layer formed by the air entering thechamber through :the

throat 2d, and, second, under full load at which time the fuel feed ismaximum, the droplets injected pierce both blankets of rotating air byaid of the turbulence caused by the third throat without beingcompletely atomized and enter the orificeZ'l of the throat 2 2, so thatas combustion takes place these relatively large droplets are directedtoward the center of the cylinder ll. The rarer portion of the fuelcharge is directed by throat 22 into the outer region of the cylindernear the top wall. Thus, we have a combustion charge in the cylinderhaving a rich center and a rarer outeriportion whichis contrary'to theaccepted theory that the mixture of air and fuel ,;should be uniform formaximum efficiency. The

efficiency theoretically lost due to the non-uni- "form mixture of thefuel charge is compensated for by the substantial elimination ofimproper surface contact burning.

Other theories have been advanced to explain the high-efficiency I haveobtained but the one given seems to satisfy the differentfactorspresent. 'It is understood, of course, that the layers of air areby no means distinct but it is believed that-thelayer produced by thethroat 22 does prevent aconsiderableportion of the solid fuel fromcontacting the chamber surface and the small amount touching the wallshas sufficient air to support combustion without smoldering. It is alsoto be understood that the mixture of air and fuel enveloped in the layerof insulating air in the chamber becomes substantially uniform beforeignition and that the richer mixture in the throat 24 is chiefly due tothe presence of the larger droplets, at full load, injected directlyintothe throat.

What I claim is:

1. A throat block for an internal combustion engine of the compressionignition type including a cylinder block having a cylinder bore and acylinder head having a cavity therein shaped at one end with a partialsurface of revolution, said throat block fitting in said cavity andhaving a complementary partial surface of revolution. registering withthe first mentioned surface .to form. a combustion chamber, and aplurality of throats leading from said combustion chamber to thecylinder bore, said throat block having a relief groove in itscylindrical periphery opening toward the wall ofthe cylinder head andhaving a second annulargroove open to said combustion chamber whereby asthe heated gases rush through the throats to the cylinder bore, saidrelief recesses will permit the throat block to increase in temperaturewithout increase in length when secured at its opposite ends by thecylinder block .and the cylinderhead.

:2. An insert element for a Diesel engine consisting of auone-piece bodyhaving: a fuel receiving chamber therein, two end surfaces adapted toengagethe engine blockand the cylinder. head respectively wherebyexpansion bythe body when heated tends to force the head and blockapart,

and a relief groove generally parallel to the plane of engagement of theengine block and cylinder head; such construction permitting the body'tobe. made exactly the, same length as the hole into which it fitsso astoavoid the building upof carbon deposits which occurs if allowance forexpansion is made.

3. The device of claim 2 in which therelief groove is annular andopensto the chamber.

4. The device. of claim.2, inwhichthe relief groove is annular and opensto the wall of the cavity in the cylinder head.

'5. The device of claim 2 in which thereare two relief grooves, oneopening into the chamber and the other opening to theside wall of thecylinder head.

RICHARD H. SHEPPARD.

